I just put a true dual exhaust on my newly purchased 88 Cougar 5.0 (47K orig miles). No Cats, 2 in pipe to Flowmasters, Air Tube re-connected at H-Pipe. Here's the problem - it seems to have started running rich. I say this because a rich exhaust odor has emerged (it has been checked again for leaks - none) and my mileage has dropped about .5 MPG.
I have limited knowledge with EFI and computer operated systems on cars (give me an FE!), so where do I start to resolve this problem? Thanks in advance.
Still using exaust manifolds or do you have headers?? o2 sensors OK and connected? They can be damaged when doing mods such as you have..
No headers. Mod was replacing everything from the exhaust manifold back. Originally didn't have the air tube hooked back up - left it hanging. Since I posted this, I've been able to check the mileage since connecting it back up via the H-Pipe and the mileage has gone back up but I'm still down about .3 mpg. Funny, since all of this my low idle is about 650 where as before it was between 700-800. Aside from all of the questioning it runs great. Just didn't want to have a potential problem I was ignoring.